Download Lakes in Texas – Why so many, why none at all?

Lakes in Texas
Lakes in Texas – Why so many,
why none at all?
• All lakes in Texas are reservoirs formed by
the damming of a stream for various
purposes…
– Flood control
– Irrigation
– Recreation
– Hydropower
– Municipal Water Supply
How Lakes form in Nature
Water flows downhill to
reach stasis. Usually this
means sea level. In order
for a lake to form,
something has to block
water’s path. In nature,
this can be done a number
of ways…
Glaciers
Gouge out huge basins
Depress the land by its sheer weight; upon melting, the
land only slowly rebounds.
Glacial lakes are characteristically…
Deep
Oligotrophic (O2 rich, nutrient sediment poor)
Cold
Low pH
Examples of Glacial Lakes
Great Bear
Great Slave
Lake Winnipeg
Great Lakes of North America
,,
Volcanoes
• Stratovolcanoes occasionally blow off their tops,
leaving a depression for water to collect, often at
high altitude.
• Volcanic lakes are characteristically…
– Deep
– Oligotrophic (O2 rich, nutrient & sediment poor)
– Cold at surface, but may be warmed by magma
from underneath)
– High pH
Examples of Volcanic Lakes
• Crater Lake, OR
• Lake Atitlan
• Lake Nicaragua
Tectonic Rifting
• Continents are subject to intense pressure from
beneath; in some places, the continental crust is
giving way, and the land is splitting apart,
forming long sinuous valleys that intercept water
from surrounding mountain ranges.
• Rift lakes are characteristically…
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–
–
–
–
Deep
Oligotrophic (O2 rich, nutrient & sediment poor)
Cold
High pH
Narrow, but not always
Examples of Rift Lakes
• Great Lakes of Africa
• Lake Baikal
• Salton Sea
Mountain Building
As continents collide with other tectonic
plates, mountains are formed, forming
hanging depressions that intercept water.
Alpine lakes are characteristically…
Deep
Oligotrophic (O2 rich, nutrient &
sediment poor)
Cold
low pH
Examples of Alpine (Synclinal) Lakes
• Flathead Lake, MT
• Spirit Lake, CO
• Lake Titicaca (Peru/Bolivia)
If mountains block water’s path to the sea, and inflow from
rivers surpasses that water loss from evaporation, then lakes
may form in deserts.
Desert Lakes are characteristically…
Shallow
Warm
Salty
Subject to huge swings in water levels
Highly alkaline
Examples of Desert Lakes
• Caspian Sea
(Russia/Azerbaijan/Iran/Turkmenistan/Kazakhst
an)
• Aral Sea (Kazakhstan/Uzbekistan)
• Great Salt Lake, UT
• Lake Chad (Chad/Niger/Nigeria)
The Aral Sea Disaster
http://observers.france24.com/en/content/20090827-death-aral-sea-soviet-irrigation-cotton-desert
weight of the water, and the fact that only enough
money was available to build an inherently weak
sand structure. This same plan, using concrete,
has been revived in 2003 by the Kazakh
government.
Vozrozdeniya Island -growing larger since 1960,
joined the mainland in 2001, and added another
cruel ingredient to the Aral disaster. Vozrozdeniya
was a Soviet Army research and biological
weapons facility until 1992, dealing reportedly in
anthrax and other nasties that now have the
potential to migrate. Ironically, Vozrozdeniya is
Russian for 'rebirth' or 'renaissance'.
The area is now constantly subject to toxic
duststorms and desertification, the people of the
area have 9 times the world average rate for
throat cancer, and infant/maternity mortality is the
highest in all of the former Soviet Union's
republics. Respiratory complications, tuberculosis
and eye diseases are also rising alarmingly.
In a deperate attempt to keep their vessels in the
shrinking Aral, channels were dredged to the
open sea. it was a futile exercise, as the sea
receded faster than the channels could be built.
The fishing industry was effectively gone by 1982,
and the canning plant processing frozen fish
brought in from other areas to keep fishermen
employed, folded in 1991.
Of the region's 73 species of birds, 70 of
mammals and 24 of fish, most have either
perished or moved on.
Vast cotton feilds, irrigated by the Kara Kum canal
and others, boosted Soviet cotton production by
Great Salt Lake
• Once much larger, North America’s largest
salt lake is a mere shadow of what it was
15,000 years ago.
Lakes in River Valleys
• As rivers meander across a
plain, they often change
course, leaving behind old
fragments of channel. These
form oxbow lakes.
• Oxbow lakes are
characteristically…
– Shallow
– Eutrophic (O2 poor, nutrient &
sediment rich)
– Variable pH
– Sickle-shaped
Examples of Oxbow Lakes
1.
1. Reelfoot Lake, TN
2. Cane River Lake, LA
3. Lake Monroe, FL
Lakes associated with Karst
Topography
• In areas of high rainfall
that are dominated by
limestone, underground
aquifers or rising
oceans may carve out
lakes in the cold watersoluble rock.
• Karst Lakes are
characteristically…
– Deep
– May be eutrophic or
oligotrophic, depending
on age and amount of
rainfall stream input
– High pH
Examples of Karst Lakes
• Lake Okeechobee,
FL
• The Lakes of Lake
County, FL
Deltaic & Coastal Lakes
• Bays occasionally become isolated from
the ocean as sediments become
deposited by rivers (deltaic) and/or by
longshore currents (coastal). These
eventually become filled with freshwater.
• Coastal Lakes are characteristically…
– Shallow
– Eutrophic
– Variable pH
Examples of Deltaic Lakes
• Lake Charlotte, TX
• Lake Anahuac, TX
Examples of
Coastal Lakes
• Big Redfish Lake, FL
Extraterrestrial Lakes
• Meteor impacts may create a crater,
which, if it occurs in an area with high
rainfall, may form a lake.
• Impact Lakes are characteristically…
– Variable in depth, amount of sediments, water
quality
– Circular in shape
Examples of Impact Lakes
• Clearwater Lakes, Quebec
• Lake Manicouagan , Quebec
What benefits do lakes give?
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Ready source of drinking water
Transportation
Fisheries
Recreation
Hydropower
Flood Control
Real Estate
Wetland restoration
Artificial Lakes – The Dark side
• Interruption of fish migration patterns
• Temperature upheaval for downstream
ecosystems
• Constant fluctuation in lake level
• Upheaval of condemned communities
• Coastal beach starvation
• Water quality issues: Recreation and
Homesteads vs. Water Quality
• Flooding
• Downgrading of wetland quality
How does water in a lake move about?
(1)
Wind → wind stress on surface (wind in
N/m2)
which creates
● mean currents
● varying currents & waves
● turbulence, leading to mixing in the vertical
How does water in a lake move about?
(2)
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•
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Heat flux ( , in W/m2) essentially of 2 types:
in 3D geometry
Heating (daytime, summer) → vertical stratification
● inhibits mixing
● shields intermediate and bottom waters
from wind-stirred mixing and surface re-aeration
- Cooling (nighttime, winter) → convective overturning
● creates vigorous mixing
● ventilates the water
(re-aeration of bottom waters by the end of winter)
So how long does water sit there?
Lakes and reservoirs differ from rivers by their greater
depths and their weaker velocities.
They therefore impound water for quite some time, and an
important characteristic of a lake is its residency time,
sometimes also called retention time.
It is defined as the average time spent by a water parcel
from time of inflow to that of outflow. The longer a fluid
parcel remains in the lake or reservoir, the more likely it
is to be subjected to local processes such as heating or
cooling, sedimentation, biological or chemical
transformations, etc.
Some examples of retention times
http://en.wikipedia.org/wiki/Lake_retention_ti
me#List_of_residence_times_of_lake_wat
er
Breaking News –
Up from the Ice Below
http://www.youtube.com/watch?v=APaBqRp
27zU
http://www.youtube.com/watch?v=XVgOiABYUE
Lakes of the World
• Go to http://en.wikipedia.org/wiki/Artificial_lake and find
the largest artificial reservoir in the world. How does it
compare to the top 15?
• Of the 15, which are glacial in origin? Which lakes are
synclinal? Which ones are rift lakes?
• What continents are missing out on the top 15? Why is
this?